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What is the “N+1 selects problem” in ORM (Object-Relational Mapping)?
...s (also rows). In other words, Car → Wheel is a 1-to-many relationship.
Now, let's say you need to iterate through all the cars, and for each one, print out a list of the wheels. The naive O/R implementation would do the following:
SELECT * FROM Cars;
And then for each Car:
SELECT * FROM Wheel W...
jQuery - setting the selected value of a select control via its text description
...
Note that jQuery 1.4 has now changed this behavior to select by value if the attribute has been specified, and only select by text if the value attribute is missing. So in this example $('select').val('Two') will select the second option in 1.3.x, bu...
How to use Git for Unity3D source control?
...for Git called Git LFS that directly deals with the below problem. You can now easily and efficiently version large binary files!
Git can work fine with 3D games out of the box. However the main caveat here is that versioning large (>5 MB) media files can be a problem over the long term as your...
What's the difference between “STL” and “C++ Standard Library”?
...long before C++ was standardised. C++ existed through the 80s, but what we now call "C++" is the language standardised in ISO/IEC 14882:2014 (and earlier versions, such as ISO/IEC 14882:2011).
The STL was already widely used as a library for C++, giving programmers access to containers, iterators a...
Reducing MongoDB database file size
...atabase().
In either case you need the space somewhere to copy the files. Now I don't know why you don't have enough space to perform a compress, however, you do have some options if you have another computer with more space.
Export the database to another computer with Mongo installed (using mon...
How do I use vim registers?
I only know of one instance using registers is via Ctrl R * whereby I paste text from a clipboard.
16 Answers
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Effects of the extern keyword on C functions
...ar.c.
Here is foo.c
#include <stdio.h>
volatile unsigned int stop_now = 0;
extern void bar_function(void);
int main(void)
{
while (1) {
bar_function();
stop_now = 1;
}
return 0;
}
Now, here is bar.c
#include <stdio.h>
extern volatile unsigned int stop_now;
void b...
Differences between unique_ptr and shared_ptr [duplicate]
... Okay
unique_ptr<T> myOtherPtr = std::move(myPtr); // Okay, resource now stored in myOtherPtr
Similarly, you can do something like this:
unique_ptr<T> MyFunction() {
unique_ptr<T> myPtr(/* ... */);
/* ... */
return myPtr;
}
This idiom means "I'm returning a manag...
Efficient SQL test query or validation query that will work across all (or most) databases
...g_table WHERE 1=0
or
SELECT 1 FROM INFORMATION_SCHEMA.SYSTEM_USERS
or
CALL NOW()
HSQLDB (tested with version 1.8.0.10)
Note: I tried using a WHERE 1=0 clause on the second query, but it didn't work as a value for Apache Commons DBCP's validationQuery, since the query doesn't return any rows
VAL...
Command copy exited with code 4 when building - Visual Studio restart solves it
Every now and then when I build my solution here (with 7 projects in it) I get the dreaded 'Command copy exited with code 4' error, in Visual Studio 2010 Premium ed.
...